1. Field of the Invention
The invention relates to a device for transmitting rotational power from a rotational power source such as an automobile engine to a rotational driven device such as a refrigerant compressor for an air conditioner. The device can rotationally separate the driven device from the rotational power source when the torque transmitted exceeds a predetermined cutoff torque level, that is, the device functions as a torque limiter.
2. Description of the Related Art
Japanese Unexamined Patent Publication (Kokai) No. 8-135752 describes a rotational power transmission device which can limit the maximum torque transmission and absorb a fluctuation in the torque. The device transmits rotational power from a rotational power source, such as an automobile engine, to a driven device, such as a compressor used in an automobile air conditioning system. The device comprises an elastic connecting member defining radially outer and inner peripheral surfaces. First and second holder members are provided to radially cooperate with each other to circumferentially hold the elastic connecting member during normal operation to transmit the rotation, and are disconnected by the deformation of the elastic connecting member when the torque on the drive shaft exceeds a predetermined cutoff torque level, for example when the drive shaft of the compressor is locked by a failure such as seizing in the compressor and the torque on the device exceeds a predetermined cutoff torque level.
In the prior art rotational power transmission device, however, the elastic connecting members cannot deform sufficiently to disengage at the predetermined cutoff torque level when the temperature of the elastic connecting member is low. Thus, the device of the prior art has a problem that it cannot disconnect the rotational power transmission when the temperature of the connecting member is low during a winter season.